Audiobook Mastering: How to Format Audio for ACX and Spotify Distribution
Mastering an audiobook? Learn the ACX audio requirements: RMS volume levels, noise floors, and file formatting.
Julian Thorne
Senior Managing Editor
"ACX maintains strict quality controls for audiobooks. If your audio files fail to meet their specifications, your audiobook will be rejected during audit."
Core Key Takeaways
- Mastering Target Volume Levels (RMS)
- Controlling the Noise Floor in Home Studios
- Formatting File Intros, Outros, and Spacing
1. Mastering Target Volume Levels (RMS)
ACX requires all files to measure between -23dB and -18dB RMS volume. This ensures consistent listening levels across all audiobook platforms.
- RMS volume levels must sit between -23dB and -18dB.
- Noise floors must remain quieter than -60dB to block background hum.
- Audio peaks must not exceed -3dB to prevent distortion.
2. Controlling the Noise Floor in Home Studios
Record in a room treated with acoustic foam to keep the noise floor below -60dB. Use high-quality dynamic microphones to block room echoes.
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3. Formatting File Intros, Outros, and Spacing
Each file must contain between 1 and 5 seconds of silent room tone at the start and end to prevent clips.
The Takeaway
Clean audio ensures listing approvals. Golden Ivory Publishing handles casting, audio editing, and quality assurance for ACX releases.
Publish at Traditional Trade Quality on Your Own Terms
Retain 100% of your royalties, copyright, and creative control while accessing world-class cover designers, CMOS editors, and formatters.
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